Method of operating electric brakes.



No. 7|2 ,994. Patented Nov.'4, I902.

F. E. CASE. METHOD OF OPERATING ELECTRIC BRAKES.

(A plication filed Apr. 24, 1902..

2 sneak Sheet 1.

(No Model.)

Inventor. Frank E.Ca$e. by M Witnesses.

"No. 7l2,994.

. Patented Nov. 4, I902. F. E. CASE. METHOD OF OPERATING ELECTRICBRAKES.

(Application fileduAr. 24, 1992;,

2 SheetsSheet 2.

(No Mpdel.)

Invntor. Q Frank E. Case.

,eiw

fltt'y s 6 s s e n UNITED STATES PATENT O FIcE.

FRANK E. CASE, OF SCHENEOTADY, NEw YORK, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

METHOD OF OPERATiNG ELECTRIC BRAKES.

SIECIFICATION forming part of Letters Patent No. 712,994, dated November4, 1 902.

Original application filed-dune 30,1897, Serial No. 642,908. Divided andthis application filed April 24:, 1902. Serial No.

v 104,480. (No model.)

To aZZ whom, it mdy concern.- I

Be it known that I, FRANK E. CASE, a citizen of the United States,residing at Schenec-l tady, county of Schenectady, State of New York,have invented certain new and useful Improvementsin Methods of OperatingElectric Brakes, (Case No. 2,853,) of which the,

following is a specification.

This application is a division of my prior In the operation of brakingdevices it often. happens that one of the axles is so far checked,

that the wheel begins to slide upon the track. This not only diminishesthe braking effect, and that very rapidly, but it also makes flat placeson the wheels and tends to increase the sliding, because when a wheelonce begins to slide the friction on the track diminishes Very rapidly.This effect increases with the speed, so that though while the wheel isrolling a good retarding effect is obtained as soon as the wheelbeginsto slip it tends to continue to slip and retards the progress ofthe car very little. It also often happens that the. other axle or axlesof the car will be acting normally at' these times, and the strain onthat, due to the slipping of the first axle, will be greatly increased.-These difficulties have been recognized and some attempt has been madeto provide forthem, but without entire success. One of the methods whichhas been applied with some success involves the use of a so-calledlimit-switch, a device for preventing the current-flow in anelectricbrake system from increasing beyond a' predetermined amount. Thedifficulty with this expedient has been that while the limitswitch couldbe adjusted for any particular current-flow it could not be changed tosuit all the varying demands of traflicx When adjusted for a dry rail,for instance, where much greater current can be permitted than where therails are greasy, it would work well solong as the rails were in thatcondition; but when the track became slippery the wheels would stick andslide, giving rise to the difficulties above pointed out.

In a braking system arranged to be operated in accordance with themethod constituting my invention no limit-switch is required, thebraking effect being regulated in the shoes themselves in such a mannerthat shoes, and the arrangement is such that these devices arecontrolled by the current in the individual motor-circuits,itbeingunderstood that the motors are used as a source of current for thebrakes. Of course other sources of current could be substituted, so faras my invention is concerned, if it were desirable to use thetrolley-current or a storage-battery current,'but ordinarily thedescribed arrangement is commercially more desirable, as is well known.

I have shown in this application two ways of shunting the shoes, one ofthese by a switch under the control of the motor-current, so arrangedthat when the motors are out of balance in the generation of current(which ordinarily is caused by their running at different speeds) theswitch will shunt the shoe corresponding to the motor running at thelower speed. This may be done either by momentarily closing theshunt-circuitand as the motor speeds up opening .it again, or it may beeffected by closing the circuit through a variable resistance andchanging the resistance in accordance with the effect desired.

The ways suggested, which will be more fully explained, are only typicalof other ways which can be utilized. For instance, in my ately releasethe revolving disk with which it the source of current for the brakes.

F F are the field-magnets. B B are the brake-shoes.

The circuitis grounded in the usual way at G.

An equalizer E is employed, and this I use to balance the currentbetween the motors in the customary way; but it has also in this casethe additional function of determining the balance of braking effect.

Referring to Fig. 1, the motors are connected in multiple, with anequalizer-circuit E joining the corresponding points between thearmature and field windings of said motors, and the said motorsoperating as generators supply current to the brake-shoes B 13 connectedin series.

D indicates an automatic switch for controlling the brake-shoes. Thelever of this switch is connected to a point between the brake-shoes Band B and through the contacts d (1 may short-circuit either of them.

0 0 indicate magnet-cores cooperating with armatu res on the lever D tooperate the'same, and these cores are provided with coils c to 0 Thecoils c and c are wound in the same direction and are connected incircuit with the armatures A and A, respectively, while the coils c andc are wound in opposite directions and are connected in theequalizercircuit. The operation of these parts is as follows: While bothof the motor-armatures A A are revolving at a substantially uniform rateor generating substantially equal electromotive forces no current willHow in the equalizer E, and the entire current of both motors will passthrough the fields to ground,

returning from ground through the brakeshoes in series back to themotors in multiple, giving a substantially uniform pull on the differentbrake-shoes. 'The currents in the coils c and 0 will be equal, and hencethe switch-lever D will be maintained in its intermediate position. If,however, one of the motor-armatu resas,for example, Ashould cease toturn for any reason, the corresponding brake-shoe B would with theordinary connections still be supplied with the full current from thearmature A so long as the latter continued to revolve; but with theconnections shown in this figure the current will or killed.

flow from the armature A through the equalizer-circuit in the'directionshown by the dotted arrow and through the coils c andc', increasing themagnetization of the core 0 and decreasing that of the core 0', so thatthe lever D will be'moved into engagement with the contact cl', therebymomentarily shortcircuiting the shoe B and releasing it. The currentflowing through the equalizer connection will divide, part flowingthrough the field-winding F in a direction to maintain its magnetizationand part flowing through the armature A in such a direction as to driveit as a motor. The speed of the armature A will therefore quickly riseuntil the two armatures are running at substantially the same speed,when the flow of current through the equalizer connection will cease,and the switch-leverD will be returned to its intermediate position. Inthe same manner it the armature A should cease to turn the brake-shoe Bwould be momentarily shortcircuited.

\Vith the apparatus arranged in the Way just pointed out the lever Dwould go first to one side and then to the other as the motor-armatures,respectively, began to run at different speeds or at speeds somaterially different as to throw the attraction of the magnets O C outof balance in the way pointed out, it being of course designed thatminor variations in the speed shall not affect the magnets. As the levertouches one or the other of the contacts cl (1 it would shunt the entirecurrent around one 'of the brake-shoes, the latter would release itsgrip, and the regulation of the braking effect would be obtained by theopening and closing of the short circuit around the shoe. arrangement,however, whichI prefer to use in practicing my invention is that shownin Fig. 2. In this the parts are marked as before, except that in placeof the electromagnets 0 C, I substitute solenoids C 0 each in serieswith one of the motor-armatures, and in addition I employ resistances RR over the contacts of which the lever D moves. The effectof thisarrangement is to be preferred to that in Fig. 1, because if, forinstance, the armature A begins to run at a less rate than A the currentin the coil 0 falls off, and the entire resistance R is connected in ashunt-circuit around the brakeshoe B. This resistance may be soproportioned that comparatively little current will flow through it, andthe magnetization of the shoe will be thus slightly reduced and the shoepartially released. If, however, the armature A continues to beretarded, part of the resistance is cut out, until should the armaturepractically cease rotation the entire resistance would be out out, andthe brake-shoe would thus be entirely released As the armature increasesits The speed,sending more and more current through the coil 0 the leverD would move over the by the armature A is highrelatlvelv to that of thearmature A the brake-shoe B will be released, and whenever, on the otherhand, the electromotiveforce generated by the ar mature A'is highrelatively to that of the armature A the brake-shoeB will be re Each ofthe axles has'a brake-shoe'B- B 00-.

' operatingwith disksl I in the usual way.

The controlling device K is also shown in plan, with a .cable from whichwires extend tothemotors and brake-shoes. The switch D, with itsresistances, is illustrated conven- In this figure I show in plan twomoto cover in theclaims hereto appended whatever inay be the characterot-the apparatus by means of which it is carried out.

That I claim as new, and desire to secure by Letters Patent'of theUnited States, is

1; The method which consists'in supplying current toelectrically-actuatedbraking devices on a plurality of car-axles, andauto- .matically releasing any one of the said braking devices wheneverthe speed of rotation of its axle is substantially less than that ofanother axle.

2. The method of braking a car or train having aplurality of axlesprovidedeach with a dynamo-electric machine and with anelectrically-actuated brake-shoe, which consists in causing saiddynamo-electric machines to supply current to actuate said brake-shoesand controlling the application of the said shoes according to therelative values of the electromotive forces generated by said-dy-'namo-electric machines.

3. The methodof braking a carer train having a plurality of axlesprovided each with a dynamo-electric machine and withanelectrically-actuated brake-shoe, which consists in causing saiddynamo'elect-ric machines to supply current to actuate said brake-shoesand controlling theapplica tion of the said shoes according to the flowof current through an equalizer connection between the saiddynamo-electric machines.

In witness whereof I have hereunto set my hand this 23d day of April,1902.

FRANK E. CASE.

Witnesses:

BENJAMIN B. HULL, HELEN ORFOND.

